This disclosure relates to thermoplastic polycarbonate compositions, and in particular to flame retardant thermoplastic polycarbonate compositions, methods of manufacture, and use thereof.
Polycarbonates are useful in the manufacture of articles and components for a wide range of applications, from automotive parts to electronic appliances. Because of their broad use, particularly in electronic applications, it is desirable to provide polycarbonates with flame retardancy. Many known flame retardant agents used with polycarbonates contain bromine and/or chlorine. Brominated and/or chlorinated flame retardant agents are less desirable because impurities and/or by-products arising from these agents can corrode the equipment associated with manufacture and use of the polycarbonates. Brominated and/or chlorinated flame retardant agents are also increasingly subject to regulatory restriction.
Nonhalogenated flame retardants have been proposed for polycarbonates, including various fillers, phosphorus-containing compounds, and certain salts. It has been difficult to meet the strictest standards of flame retardancy using the foregoing flame retardants, however, without also using brominated and/or chlorinated flame retardants, particularly in thin samples. In addition, non-brominated and/or non-chlorinated flame retardants can adversely affect desirable physical properties of the polycarbonate compositions, particularly impact strength.
Polysiloxane-polycarbonate copolymers have also been proposed for use as non-brominated and non-chlorinated flame retardants. For example, U.S. Application Publication No. 2003/015226 to Cella discloses a polysiloxane-modified polycarbonate comprising polysiloxane units and polycarbonate units, wherein the polysiloxane segments comprise 1 to 20 polysiloxane units. Use of other polysiloxane-modified polycarbonates are described in U.S. Pat. No. 5,380,795 to Gosens, U.S. Pat. No. 4,746,701 to Kress et al., U.S. Pat. No. 5,488,086 to Umeda et al., and EP 0 692 522B1 to Nodera, et al., for example.
While the foregoing flame retardants are suitable for their intended purposes, there nonetheless remains a continuing desire in the industry for continued improvement in flame retardance, including a need for polycarbonate compositions having improved flame retardance without use of brominated and/or chlorinated flame retardants. It would also be advantageous if improved flame retardance could be achieved without substantial degradation of properties such as impact strength.